Numerous devices have been constructed for monitoring fluid flow through pipes. In some applications, it is very crucial to known when fluid is flowing. One such application involves marine cooling systems.
Many boat engines rely for cooling on the water supporting the boat. Normally water is driven from outside the boat through tubing to a heat exchanger where the engine heat is transferred to the cooling water, and the water is pumped out of the boat.
This can be a very efficient way for cooling a marine engine, but there are drawbacks. Cooling pumps can malfunction and debris in rivers, lakes and the ocean may be sucked into the cooling system and block the flow of cooling water to the engine. If this happens, there is a danger that the engine will overheat quickly and be damaged. Therefore, it is crucial to know immediately when fluid stops in a marine cooling system.
Obviously, there are many other applications in which it is important to detect whether fluid is flowing. The present invention has applications in the other technologies even though it was primarily designed for marine engine cooling systems.
If there is a blockage in the cooling system, there will be a change in pressure. A pressure gauge could be used to monitor such changes but there are some drawbacks with pressure gauges. First, many have numerous moving parts, and they can be delicate so that the debris which would clog the cooling pipes might also jam the pressure switch. Moreover, a pressure gauge may read increased or decreased pressure during a tube blockage depending on the location of the gauge relative to the block.
Flow detectors, sensitive to the flow of fluid through the system, could also be employed in lieu of pressure detectors. Many exist in the prior art. One conventional system uses a paddle in the path of fluid flow. The paddle is biased so that it is normally across the path of fluid flow. However, once flow starts, the paddle either aligns itself parallel to the fluid flow or moves against the wall of the fitting.
In certain conventional systems, the paddle is mounted on a shaft which extends through the tubing. The extension of the shaft is connected to a switch which detects whether the paddle is across the normal flow of fluid (the "no-flow" position) or parallel to the fluid flow (the flow position). For example, see Liddell, U.S. Pat. No. 3,360,621.
One major problem with prior art fluid flow devices was that the shaft mounting the paddle extended through the tubing walls. Seals were necessary in order to prevent fluid from leaking from the tubing past the shaft. This is especially true for oceangoing vessels because salt water can be extremely corrosive. Therefore, one of the objects of the present invention is to disclose and provide a flow sensor which does not rely on connections through the tubing walls to work.
Mounting the switch in the tubing with wires projecting through the tubing wall to the indicator apparatus creates two problems. Wires extending through the housing walls subjects the housing to leaks. Moreover, salt water and even fresh water can rapidly corrode a switch, especially because there will most likely be parasitic currents which can speed the corrosion of the switch. Therefore, an object of the present invention is to disclose and provide a switch mounted outside of the fluid flow which is sensitive to the orientation of the paddle with no connection from the paddle to the switch through the tubing walls.
Further objects of the present invention include disclosing and providing a flow detector in which the switch is mounted outside of the fluid carrier, the means for detecting fluid flow is in the carrier and there is no physical connection between them.
Other problems in the prior art exist. The paddle may have to distinguish between low flow and no flow. If a standard sized flow detector is to be connected to tubing of different diameter, the flow through the detector will be slower than the flow through small diameter tubing. Low flow may fail to pivot the paddle. Therefore, another object of the present invention is to disclose and provide a means for adjusting the cross-section through the tubular section at the paddle to direct the fluid to the side of the tubular section adjacent the paddle to speed fluid flow by the paddle.
Very fast fluid flow can create difficulties. If the paddle has a pivot point mounted in a bushing in the tubular section, fluid passing the bushing creates a vacuum in the indentation tending to pull the pivot on the paddle into the indentation. This cam jam the paddle in the flow position such that if flow stops, the paddle will not return to the no-flow position rendering the device ineffective at detecting flow stoppages. Therefore, another object of the present invention is to disclose and provide means for relieving the vacuum in the indentation so that the paddle will not jam in the flow position.
Other objects of the present invention include disclosing and providing a reliable system highly sensitive to low fluid flow. In that regard, a further object is to disclose and provide a system where corrosion is eliminated as much as possible. These and other objects will become evident in the following description of the invention.